Purpose: There is a need for artificial intelligence which nurtures human intelligence as the prevalence of dementia and collapse of intelligence of human beings has become a social problem. Purpose of this study is to develop intervention technologies for maintaining cognitive health of older adults. Methods: The method named the Coimagination Method (CM) was proposed and has been developed in order to achieve goal. Conversation assistive technologies have been developed and tested based on the method. Results: The state of the art of the group conversation support system, and regular series of group conversation sessions for full-years with insights for healthy older adults are described in detail. Participatory approach has been applied to the design process for simultaneous research and implementation of the service. Both participants and practitioners have been maintaining their cognitive health for independent living. Conclusion: Findings imply that there exist potentially preventive types of dementia and intervention should be applicable for such types. Ways of thinking and living are gently intervened through understanding of personal values and broadening minds, which lead to improved quality of life.